Damaged Villages after loading with 13w16a and returning back to 1.5.1

Bug:
After loading a World with Version 13w16a and loading the same World later with 1.5.1 again, 2 from 6 checked Villages were loaded wrong or damaged.

Recreate: Haven't find out yet, because it is a pretty rare and random Bug.

What kind of Damage:
-Houses cut
-Houses and Blocks placed wrong
-Houses and Blocks disappeared

Note:
World Created in: 1.2.5
Affected Villages first discovered in 1.2.5 and ~1.4.5
Not happend in other backup. (same World)
It seems like it is a rare random bug.
Reload does not solve the problem.
Self build things are (at first view) not effected by this bug.